1. Load balancing for SIP media applications Fostel 2007 Raphael Coeffic (raphael.coeffic@tekelec.com)

2. Problem statement Media servers consume usually a lot of ressources (SEMS is not an exception). It is then more common to have a media server farm. How are we supposed to implement the load balancing in such a farm?

3. Different solutions At the IP layer:  use traditional IP load balancers (UDP/TCP).  You will need at least some basic support from the SIP side to get that to work.  You could have troubles with NATs or firewalls. SIP-wise:  leverage SIP routing to spread the requests.  You will need a very fast SIP proxy / load balancer.  Guess what? SER is doing more than 5k transactions / second.

4. SIP load balancing Background  Media applications are mostly addressed by request URI (as recommended by relevant RFCs). How?  Round-robin style:  You may also want to implement some more complicated stuff, maybe based on load feedback.  Requests are just spread, and the load balancer does not need to stay in the signaling path.  Hashing based method:  Some value in the SIP message is hashed to determine the target.  The load balancer could even sit on the signaling path and stay stateless.  Statistics sometimes play tricks if the population is small.

5. Example: Voice2email 1. INV raphael@voicemail.iptel.org 2. INV raphael@voicemail.iptel.org Round-robin load balancing

6. Example: PSTN conferencing 1. Dial “0800 CONFERENCE“ 2. INV conf@iptel.org 3. INV conf@iptel.org 4. Transfer call to: 1234@conf.iptel.org 5. INV 1234@conf.iptel.org Hashing based load balancing

7. Thank you! Questions? Fostel 2007 Raphael Coeffic (raphael.coeffic@tekelec.com)